Bullet lubrication formula

ABSTRACT

A composition for bullet lubrication that comprises an admixture of carnauba wax and beeswax in combination with mineral oil, silicone oil, metal-containing greases, molybdenum disulfide and graphite. The application of lubricants may be made to the aft portion of the surface of the bullet.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to lubricants for and lubrication of projectiles such as bullets.

2. Description of the Related Art

Bullets fired from pistols, rifles and other guns are exposed to extremes of temperature and pressure. The bullets from a high-powered rifle may reach velocities on the order of 3,000 to 4,000 feet per second (914 to 1220 m/s) and may be subjected to peak pressures of 50,000 pounds per square inch (34,500 N/cm²). One of the more important problems with unjacketed bullets is known as “leading”, which is the phenomenon of lead from the bullet being deposited, by melting, friction, or otherwise, on the surfaces of the bore of a gun barrel. Lead fouling, fouling by other metals and other fouling make it difficult to fire the bullets accurately and consistently even with exactly matched loads, and even from a fixed position.

In an attempt to overcome the detrimental effects of lead fouling, commercial ammunition manufacturers and individual hand loaders have adopted various expedients. One of these consists of jacketing the lead bullet with gilding metal, such as a copper base alloy nominally containing 5 percent zinc. Unfortunately, while the jacketed bullet is a significant advance in the art, it too has disadvantages, the more important of which include copper fouling; i.e., the transfer of copper from the bullet to the inner surface of the barrel in a manner analogous to lead fouling. Aluminum jacketed bullets have been introduced for pistols to solve the metal deposition problem at reduced cost. Unfortunately, this round is not suitable for rifles where bullet velocities are high enough to result in aluminum fouling. These improvements thus have not provided a complete answer to the metal fouling problem.

In addition to metal fouling, the combustion of the propellants frequently leaves a residue in the bore. This is also undesirable as it can affect the accuracy and consistency of the firearm. The residue may also be hygroscopic and/or corrosive, potentially contributing to pitting of the barrel that further affects accuracy.

Another concern is friction between the bore and the bullet. Previously, friction was considered to be such a small factor in projectile ballistics that it was often ignored. However, it is now understood that even a relatively low projectile velocity can create sufficient frictional heat to actually melt the surface of a lead bullet, causing leading in the barrel and emission of lead vapor from the barrel. Furthermore, even microscopic imperfections in the bore can cause small particles of metal jackets, zinc bases or lead to become embedded in the surface of the bore. Continued firing only creates additional deposits which can shift positions within the barrels resulting in erratic trajectories.

In order to reduce the effects of friction, including metal fouling, a variety of lubricants have been employed. Some attempts at providing a bullet lubricant have not been particularly successful, such as those based on paraffin wax or lubricants not originally developed for use in lubrication of projectiles. The lack of success of such lubricants may arise from the environment encountered in the discharge of a firearm, which may include velocities as high as 3,000 to 4,000 feet per second (914 to 1220 m/s), and pressures as great as 50,000 pounds per square inch (34,474 N/cm 2). Many of the prior art wax lubricants, including those intended for ballistics applications, are unstable at the temperatures and pressures encountered by a bullet rapidly traveling through a gun barrel.

Another problem of bullet lubricants has been that they are often soft and greasy or tacky. This can result in the accumulation of grit and other particulates, and the lubricant and embedded grit may accumulate in the magazine, cylinder, receiver and elsewhere in the firearms. Such accumulations may contribute to jamming and other malfunctions of the firearms. Accumulation of the lubricant in loading or reloading equipment can similarly be problematic.

Hard, non-tacky lubricants such as certain molybdenum-based bullet lubricants solve some of these problems. However, in some cases, these lubricants may chip or flake off.

One approach to remedy this problem has been to provide one or more annular or other recesses in the surface of the bullet, but this results in a bullet that does not have a smooth, uninterrupted surface, and increases the cost of producing the bullet. Another approach involves etching the surface of the bullet and embedding the lubricant in the recesses so created. Again, this increases the cost of bullet production and leaves the bullet with a rough, rather than smooth surface. Yet another approach involves providing a reservoir of lubricant within the bullet together with channels that allow the lubricant to escape from the reservoir to the surface of the bullet when it is fired. This again adds cost and complexity to bullet production.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides a method of lubricating a bullet in which a thin film of lubricant is applied in a band that may be applied from about the ogive of the bullet to the rear end thereof. In another aspect, the lubricant has a tenacity that permits it to be inserted into the casing while retaining a sufficient quantity of lubricant on the bullet or other projectile. In another aspect, a lubricant is provided that has a high concentration of carnauba wax. In other aspects, the high-carnauba lubricant includes components such as silicone oil, paste or grease, graphite, beeswax, molybdenum disulfide and lithium and/or other metal-containing greases.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation of a prior art, unlubricated cartridge for a firearm with parts broken away.

FIG. 2 is a side elevation with parts broken away of a cartridge with a band of lubricant covering the rear portion of the bullet.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

In addition to pistols and rifles, a variety of projectile-firing weapons can benefit from proper projectile lubrication. These other weapons include machine guns, tank and naval cannons, howitzers and the like. For the sake of simplicity, although the invention has such broader application, small arms and small arms munitions will be used to illustrate the invention.

As shown in FIG. 1, which is labeled “Prior Art,” a modem center-fire pistol cartridge 10 comprises a bullet 12 and a casing 14. A primer 16 is mounted in an aperture in the base 18 of the casing 14. The propellant charge 20 is contained within the casing 14.

The bullet 12 comprises a rounded nose portion 22 that blends into a rear, cylindrical body 24. The cylindrical body 24 of the bullet has a diameter approximately equal to the caliber of the weapon in which it is intended to be used. Some bullets depart from the foregoing structure in that the rearward portion of the cylindrical body 24 of the bullet 12 tapers to a smaller diameter. Such bullets are often referred to as boat-tailed. A significant portion of the cylindrical body 24, however, retains a diameter approximately equal to the bullet diameter.

For both pistol and rifle rounds, the portion of the bullet 12 that is seated within the cartridge 14 typically includes a portion having a diameter equal to the caliber of the weapon, with the exception of a possible boat-tailed section, while the portion extending forward from the casing 14 tapers down to the nose. Accordingly, most of the portion of the bullet 12 contained within the casing 14 is of the caliber of the weapon while the portion forward of the casing is of a diameter less than the bullet caliber.

According to one embodiment of the invention, and as shown in FIG. 2, a band of lubricant may be applied to the rear portion 26 of the bullet 12. The coating may include the portion of the bullet 12 that is intended to be contained within the casing 14, the portion of the bullet 12 that has a diameter approximately equal to the caliber of the firearm in which it is to be used, or the portion of the bullet 12 that contacts the barrel of the firearm during firing. In most cases, the point along the surface of the bullet 12 behind which lubricant is applied will generally be mostly, if not entirely, within the casing 14 and will not be much forward of the casing 14. After lubrication, the bullet 12 may thereafter be inserted into the casing 14. The forepart or nose 22 of the bullet may be, but need not be, coated with the lubricant, as this part does not contact the bore of the firearm. This reduces the amount of lubricant actually used and decreases the amount of vaporized lubricant discharged into the air when the bullet is fired.

After insertion of the bullet 12 into the casing 14, the band of lubricant, or at least the portion thereof that is within the casing 14, is protected against removal from the bullet by the casing 14. In addition, as the outside diameter of the casing of many bullet cartridges is greater than the maximum diameter of the bullet 12, the casing can provide some protection against removal of the lubricant for a short distance forward of the mouth of the casing 14. Deposit of the lubricant in the magazine, breach or other mechanisms within the firearm is reduced because the lubricant does not come into contact with such mechanisms during the loading or firing process. As the lubricated portions 26 of the bullets 12 are the only portions that contact the interior of the bore of the firearm, the necessary lubrication is provided to reduce fouling of the bore as well as to reduce undesired frictional effects resulting from movement of the bullet along the length of the bore.

There are many possible methods of applying a band of lubricant to the exterior, rear portion of a projectile. One simple method involves dipping the desired portion of the projectile 12 into the lubricant, removing it therefrom and allowing it to cool. This can be accomplished by hand, or the process may be automated. as by using a mechanism that grips the nose or other portion 22 of the projectile 12 and dips the rear portion 24 into the lubricant. For lubricants such as those described herein, the lubricant may need to be melted before dipping. The projectiles 12 may be preheated before dipping them in the pan to facilitate the dipping process.

Pan coating may also be used. According to this method, the projectiles 12 are set upright in a pan with a planar bottom surface. The lubricant is then flowed around the bullets to the desired depth. The pan may be drained before the projectiles are removed. Multiple coats may be used if a single coat does not produce the desired thickness. In coating the projectiles 12, the bottom surface of the projectile may be coated as well as the exterior of the cylindrical portion 24, since this portion does not contact the mechanisms of the firearm, and hence lubricant cannot be abraded from or transferred to the mechanisms of the firearm from this portion of the projectile 12.

Those skilled in the art will recognize that other methods for providing a band of lubricant about the rearward portions of a bullet may also be used.

Not all lubricants are suitable for use with the band lubrication process of the present invention. As lubrication of the bullet 12 occurs prior to insertion of the bullet into the casing 14, if the lubricant is too soft and lacking in adherence to the bullet 12, an excessive amount may be removed as the bullet is pressed into the casing. Likewise, a lubricant that is too brittle or prone to flaking may peel or flake away from the bullet 12 as it is inserted into the casing. Lubricants of the type described below and in my prior U.S. Pat. No. 4,731,189 of Mar. 15, 1988 entitled “Bullet Lubricant and Method of Compounding Said Lubricant” form a suitable film of lubricant the thickness of which can be kept to under 0.002-0.003 inches (0.05-0.08 mm).

Test rounds according to the present invention were prepared using band lubrication of bullets as described herein, and were found to retain sufficient lubricant after insertion of bullets 12 into casings 14.

Bullets that have been band lubricated with the lubricant of my prior patent and with lubricants according to the present invention reduce the accumulation in the bore of the typical residues left by unlubricated, but otherwise equivalent, rounds. In fact, the amount of such residue left after firing of a series of unlubricated rounds has been observed to be reduced by the firing of such band-lubricated rounds. Copper or other metal fouling has also been observed to be reduced after firing of such band-lubricated bullets. Another effect that has been observed firing such lubricated rounds as compared to firing of unlubricated rounds is reduced barrel temperature. Groupings from bench-fired, band-lubricated rounds also have been observed to be tighter than for firing of equivalent unlubricated rounds.

Lubricants according to one embodiment comprise an admixture of mineral oil, silicone oil or paste, such as MOLYKOTE® 44 (a phenyl methyl silicone paste), graphite, such as graphite flake products sold by Dixon Microfine Graphite of Lakehurst, N.J., molybdenum disulfide, such as molybdenum disulfide powder manufactured by Dow Coming Corp. of Midland, Mich. and sold under the brand name MOLYKOTE® Z, and metal-containing grease, such as MOLYKOTE® BR-2 (a molybdenum disulfide-containing lithium soap base grease) and MOLYKOTE® G-N (a molybdenum disulfide-containing mineral oil base paste) products also manufactured by Dow Corning Corp., and waxes, such as beeswax and carnauba wax. For purposes of reducing greasiness/tackiness of the formulation while avoiding undue chipping or flaking, carnauba wax in amounts of 29 percent to 43 percent by volume are used.

The term “silicone oil” is used herein to include compositions that may also be referred to as pastes, as is the case with the MOLYKOTE® product, or as greases. Similarly, the metal-containing greases may be alternatively characterized as pastes, as is the case with the MOLYKOTE® G-N product.

Several formulations have been compounded with carnauba wax concentrations in the range recited above. These formulations are set forth in Tables I and II below, with the corresponding concentration of the components being given in parts by volume in Tables III and IV. TABLE I A B C D E F G H I J K L Mineral 0.5 1 5 3 1 1.5 5 0.5 5 1 1 1 Oil Silicone 0.5 1 2 1.5 2 0.5 2 1 1 0.5 2 1 Oil Microfine 1 1.5 3 1 3 1.5 2.5 1.5 1.5 1.5 1.5 1 Graphite Camauba 6 10 17 12 12 11 14 10 10 10 10 10 Wax Beeswax 5 11 16 12 10 14 10 11 11 11 11 11 Molybdenum 0.5 1 2 1.5 2 1 2 1 1 1 1 1 Disulfide Molykote ® 1 2 4 4 1.5 2.5 3 2 2 2 2 2 BR-2 Molykote ® 1 2 4 3 1.5 2.5 4 2 2 2 2 2 G-N

TABLE II M N 0 P Q R S T U V W Mineral Oil 1 1 1 1 1 1 1 1 1 1 1 Silicone Oil 1 1 1 1 1 1 1 1 1 1 1 Microfine Graphite 3 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 15 15 Carnauba Wax 10 9 14 10 10 10 10 10 10 10 10 Beeswax 11 11 11 5 16 11 11 11 11 11 11 Molybdenum 1 1 1 1 1 0.5 2 1 1 1 1 Disulfide Molykote ® BR-2 2 2 2 2 2 2 2 1 4 2 2 Molykote ® G-N 2 2 2 2 2 2 2 2 2 1 4

Tables III and IV below provide the corresponding percent by volume of the various formulations of Tables I and II. The percentages for a particular formulation may not add up to one hundred percent due to rounding. TABLE III A B C D E F G H I J K L Mineral 3.2% 3.4% 9.4% 7.9% 3.0% 4.4% 12% 1.7% 15% 3.5% 3.3% 3.5% Oil Silicone 3.2% 3.4% 3.8% 4.0% 6.1% 1.5% 4.7% 3.5% 3.0% 1.7% 6.6% 3.5% Oil Microfine 6.5% 5.1% 5.7% 2.6% 9.1% 4.4% 5.9% 5.2% 4.5% 5.2% 4.9% 3.5% Graphite Camauba  39%  34%  32%  32%  36%  32%  33%  34%  30%  34%  33%  34% Wax Beeswax  32%  37%  30%  32%  30%  41%  24%  38%  33%  38%  36%  38% Molybdenum 3.2% 3.4% 3.8% 4.0% 6.1% 2.9% 4.7% 3.5% 3.0% 3.5% 3.3% 3.5% Disulfide Molykote ® 6.5% 6.8% 7.6%  11% 4.6% 7.3% 7.1% 6.9% 6.0% 6.9% 6.6% 6.9% BR-2 Molykote ® 6.5% 6.8% 7.6% 7.9% 4.6% 7.3% 9.4% 6.9% 6.0% 6.9% 6.6% 6.9% G-N

TABLE IV M N 0 P Q R S T U V W Mineral Oil 3.2% 3.5% 3.0% 4.3% 2.9% 3.5% 3.3% 3.5% 3.2% 3.5% 3.2% Silicone Oil 3.2% 3.5% 3.0% 4.3% 2.9% 3.5% 3.3% 3.5% 3.2% 3.5% 3.2% Microfine Graphite 9.7% 5.3% 4.5% 6.4% 4.5% 5.2% 4.9% 5.3% 4.8% 5.3% 4.8% Carnauba Wax  32%  32%  42%  43%  29%  34%  33%  35%  32%  35%  32% Beeswax  35%  39%  33%  21%  46%  38%  36%  39%  35%  39%  35% Molybdenum Disulfide 3.2% 3.5% 3.0% 4.3% 2.9% 1.7% 6.6% 3.5% 3.2% 3.5% 3.2% Molykote ® BR-2 6.5% 7.0% 6.0% 8.6% 5.8% 6.9% 6.6% 3.5%  13% 7.0% 6.4% Molykote ® G-N 6.5% 7.0% 6.0% 8.6% 5.8% 6.9% 6.6% 7.0% 6.4% 3.5%  13%

As illustrated in Tables III and IV above, the total amount of mineral oil used ranges from 1.7 to 15 percent by volume of the composition. Silicone oil is used in amounts of 1.5 to 6.6 percent, graphite is used in amounts of 2.6 to 9.7 percent, carnauba wax is used in amounts of 29 to 43 percent, beeswax is used in amounts of 21 to 46 10 percent, and the metal-containing greases are used in amounts of 9.4 to 19 percent.

The foregoing tables provide guidance that should enable those skilled in the art to compound lubricants that have sufficient tenacity, that is that adhere sufficiently to the bullet, that a sufficient amount of the lubricant remains on the portion of the bullet inserted into the casing for proper lubrication and anti-fouling purposes, and yet that lack greasiness or tackiness that may attract grit or may accumulate excessively on loading equipment and in the cylinder, receiver, etc. of a firearm, and that are not prone to chipping or flaking off during normal handling.

The lubricants of the above tables may be compounded by heating and mixing them together. As the beeswax and carnauba wax are not liquid at room temperature the waxes may be melted and the other components may then be mixed in. Once a uniform mixing of the components has been achieved, the lubricant is ready to be coated onto the bullets.

Although the invention has been discussed above in connection with various embodiments, it will be appreciated that it is susceptible of changes and/or modifications within the scope of the inventive concept within the scope of the appended claims. 

1. A bullet lubricating composition comprising 29% to 43% of carnauba wax in admixture with 21% to 46% beeswax, 1.7% to 15% mineral oil, 1.7% to 6.6% silicone oil, 2.6% to 9.7% graphite, 1.7% to 6.6% molybdenum disulfide powder and 9.2% to 19% metal grease, all by volume.
 2. The composition of claim 1 wherein the metal grease comprises two metal-containing greases mixed with the remaining components and wherein the two metal greases comprise the molybdenum disulfide-containing lithium soap based grease sold under the trademark MOLYKOTE® BR-2 PLUS and the molybdenum disulfide-containing mineral oil based paste sold under the trademark MOLYKOTE® G-N.
 3. The composition of claim 2 wherein the silicone oil comprises a phenyl methyl silicone past.
 4. The composition of claim 3 wherein the silicone oil is that sold under the trademark MOLYKOTE®
 44. 5. A bullet lubricating composition comprising 29% to 43% by volume of carnauba wax out of a total percentage of carnauba and beeswax of 57% to 74% by volume, the composition further comprising mineral oil, silicone oil, graphite, molybdenum disulfide powder, and metal-containing grease.
 6. The bullet lubricating composition of claim 5 wherein the mineral oil comprises 1.7% to 15%, the silicone oil comprises 1.7% to 6.6%, the graphite comprises 2.6% to 9.7%, the molybdenum disulfide powder comprises 1.7% to 6.6% and the metal-containing grease comprises 9.2% to 19% of the composition by volume.
 7. The composition of claim 6 wherein the metal-containing grease comprises two metal-containing greases mixed with the remaining components and wherein the two metal greases comprise the molybdenum disulfide-containing lithium soap based grease sold under the trademark MOLYKOTE® BR-2 PLUS and the molybdenum disulfide-containing mineral oil based paste sold under the trademark MOLYKOTE® G-N.
 8. The composition of claim 7 wherein the silicone oil component comprises a phenyl methyl silicone paste.
 9. The composition of claim 8 wherein the silicone oil comprises the phenyl methyl silicone paste sold under the trademark MOLYKOTE®
 44. 10. A method of lubricating a projectile comprising the step of applying a film of lubricating composition to the rear portion only of the surface of the projectile.
 11. The method of claim 10 wherein the rear portion of the projectile is defined by the portions of the projectile behind the first point at which the diameter of the projectile is at least as great as the bore of a weapon suitable for its use.
 12. The method of claim 10 wherein the rear portion of the projectile is defined by that portion extending rearward from the ogive of the projectile.
 13. The method of claim 10 further comprising the step of inserting the projectile into a casing such that the lubricated portion of the bullet is contained within the casing.
 14. The method of claim 10 wherein the lubricating composition comprises 57% to 74% by volume of waxes, of which 29% to 43% by volume is carnauba wax and the remainder of the waxes is beeswax, the composition further comprising mineral oil, silicone oil, graphite, molybdenum disulfide powder, and metal-containing grease.
 15. A method of lubricating a projectile having forward end comprising the nose of the projectile and a rearward end remote from the nose, at least a portion of the rearward end being insertable into a shell casing, comprising the steps of: formulating a lubricating composition suitable for application as a lubricant film on the surface of said projectile; applying a film of said lubricating composition to the rear portion only of the projectile; and assembling the projectile and the casing to form a cartridge.
 16. The method of claim 15 wherein the rear portion of the projectile is defined by the portions of the projectile behind the first point at which the diameter of the projectile is at least as great as the bore of a weapon suitable for its use.
 17. The method of claim 15 wherein the rear portion of the projectile is defined by that portion extending rearward from the ogive of the projectile.
 18. The method of claim 15 wherein the rear portion of the projectile is defined by that portion of the projectile that is inserted into the casing.
 19. The method of claim 15 wherein the lubricating composition comprises 57% to 74% by volume of waxes, of which 29% to 43% by volume is carnauba wax and the remainder of the waxes is beeswax, the composition further comprising mineral oil, silicone oil, graphite, molybdenum disulfide powder, and metal-containing grease.
 20. A ballistic cartridge comprising: a projectile having a forward end portion adjacent the nose thereof and a rear end portion at the opposite end thereof; a film of lubricating composition coated onto the surface of only the rear end portion only of said projectile; a casing including a propellant chamber, the casing having a mouth at one end for receiving the projectile, the rear end portion of the projectile being inserted into the casing in gripping engagement with inner wall portions of the casing, at least a portion of the film of lubricating composition being applied to that portion of the projectile that is inserted into the casing. 